Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’-Thimble Cactus

Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 7-18-18, #473-13.

Thimble Cactus

Mammillaria vetula subsp. gracilis 

‘Arizona Snowcap’

mam-mil-AR-ee-uh  VET-uh-luh  GRASS-il-is


Mammillaria gracilis var. fragilis

mam-mil-AR-ee-uh  GRASS-il-is  FRAJ-ih-liss

Mammillaria vetula subsp. gracilis (Pfeiff.) D.R.Hunt is the correct and accepted name for this subspecies of Mammillaria vetula. It was named and described by David Richard Hunt in Mammillaria Postscripts in 1997. It was first named Mammillaria gracilis by Ludwig Karl Georg Pfeiffer in Gartenzeitung in 1838.

Mammillaria gracilis var. fragilis A.Berger was named and described by Alwin Berger in Kakteen in 1929. 

Mammillaria vetula Mart. was named and described by Carl (Karl) Friedrich Philipp von Martius in Nova Acta Physico in 1832.

So, I suppose, according to date named, the species Mammillaria vetula wins the prize…


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 7-18-18, #473-14.

I bought this cactus from Lowe’s on July 18, 2018. The label says is a Mammillaria gracilis fragilis monstrose. Mammillaria gracilis subsp. fragilis is now a synonym of Mammillaria vetula subsp. gracilis.

The label says:

“Mammillaria gracilis v. fragilis monstrose is a special monstrose cultivar of the charming miniature Mammillaria gracilis fragilis. Clusters prolifically to form mats. Satiny creamy yellow flowers in the late winter. Protect from frost to prevent scarring. Provide bright light; hardy to 20F; to 4” tall. Water thoroughly when soil is dry.


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 7-8-18, #473-15.

This plant was bulging in a small 11 oz. pot that was 3 1/4” tall x 3 1/2” diameter. The cluster of plants was 2” tall x 5” wide.


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 7-8-18, #473-16.

Family: Cactaceae
Origin: Nursery origin. Species from Mexico
Zones: USDA Zones 10a-11 (30 to 40° F)
Size: Hmmm…
Light: Sun to part shade. Looks best when in full sun but needs to be introduced gradually.
Soil: Very well-draining soil. Potting soil with additional grit and pumice or perlite. (2-1-1 ratio).
Water: Water sparingly during the summer and barely in the winter.

Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 7-8-18, #473-17.

Llifle (Encyclopedia of Living Forms) says “Mammillaria ‘Arizona Snowcap’ is a monstrous form of Mammillaria vetula subsp. gracilis which is characterized by densely packed separate clusters of spines. It looks so different to the wild species that it isn’t easy to realize that they are related. This cultivar offsets generously from sides and upper part of plant, which gives it a snowball appearance. Mature group can reach 10-12 cm in diameter and 6-8 (10) cm in height.”


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 7-29-18, #487-70

They do best and look their best when grown in full sun but are rarely grown that way in cultivation. It is essential that they become acclimated to full sun gradually so the plants won’t burn.


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 8-18-18, #498-5.


Mammillaria vetula subsp. gracilis on 8-26-18, #499-28.

I put the Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on the back porch so it could get more sun maybe it will become more white. We shall see,

Plants should be grown in a very well draining mix of 2 parts potting soil amended with 1 part grit (chicken grit) and 1 part pumice or perlite. The best cactus and succulent growers and enthusiasts recommend using pumice over perlite if it is available. Here, it isn’t available unless I buy online, so I just use perlite. It depends a lot on the potting soil as some brands already have plenty of perlite. If you use pumice it can take the place of the grit as well and you can mix it 50/50.


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ at 1 5/8″ tall x 5 1/8″ wide on 10-10-18, #519-54.

I had to move the potted plants inside for the winter on October 10 because the forecast was calling for an “F” in a few days and the nighttime temperatures were getting cooler. I usually measure the cactus and succulents when I bring them inside. This cluster of plants measured 1 5/8″ tall x 5 1/2″ wide.

It is recommended that they watered sparingly during the summer and barely it at all during the winter months. I usually go over my cactus and succulents at the same time as my other potted plants, but I go over them quickly. 


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 11-29-18, #534-28.

November 29 was a nice spring-like day, so I took the cactus to the back porch for a photo shoot. I was working on a post to show the difference between the cactus in my collection.


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ on 11-29-18, #534-29.

I had a Mammillaria vetula subsp. gracilis before that was much different. When I first brought this plant home none of the offsets were as thickly covered as a few are now but I still knew it was different than the previous one. In fact, there was one next to it at Lowe’s when I found this one. I have no idea why only a few offsets spines are thicker and the others aren’t. It is going to be an interesting plant to watch.


Mammillaria vetula subsp. gracilis ‘Arizona Snowcap’ close-up on 12-1-18, #535-21.

The species, Mammillaria vetula, has 1-2 central spines and at least 25 radial spines. The subspecies often lacks the central spines and only has 11-16 radial spines. The plant I had before also had much longer spines. Its flowers are also shorter. I noticed the areoles on the top have a small tuft of wool but not so much on the lower parts. It is hard to tell if this plant has central spines.

There isn’t much online about this cultivar yet, but maybe someday there will be more.

I hope you enjoyed this page and maybe found it useful. If you have any comments, questions or suggestions, I would like to hear from you. Please click on “like” if you visited this page. It helps us bloggers stay motivated. 🙂 You can check out the links below for further reading. The links take you directly to the genus and species of this plant.